Isomerization process



iinite tates Patch ISOMERIZATION PROCESS Morris Feller, Park Forest, 11]., and Harry M. Brennan,

Hammond, and Herman S. Seelig, Valparaiso, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Mar. 25, 195 8, Ser. No. 723,628

15 Claims. (Cl. 260-683.2)

As an end product and also as an intermediate product in various petroleum and petrochemical refining processes, internal olefins, that is, olefins with the double bond other than between carbon atoms at the terminus of a carbon chain, are often preferred to terminal olefins, that is, olefins with the double bond between carbon atoms at the terminus of a carbon chain. For example, in the catalytic alkylation of isobutane with butenes to form high-octane components for blending into motor fuels and/ or aviation gasolines, it has been found that alkylate produced using butene-2 as feed has a substantially higher Research octane number than alkylate produced using butene-l.

Various processes are available for isomerizing terminal olefins to internal olefins, but such processes generally suffer from one or more limitations, such as, for example, unfavorable equilibrium conditions, excessive cracking of olefin, undesired polymerization of olefin,- relatively slow reaction rates, relatively expensive catalyst systems, excessive contaminants in isomerized product, feed stock preparation problems, and the like. It is therefore an object of the present invention to provide a process for the isomerization of straight-chain terminal olefins to straight-chain internal olefins, which process employs a liquid catalyst and is capable of operating at favorable equilibrium temperatures without suffering from the above-mentioned limitations. It is also an object of the present invention to provide a catalyst and a promoter for such process. These and other objects of the present invention will become apparent as the detailed description proceeds.

The primary process condition limiting maximum conversion of terminal olefins to internal olefins is reaction temperature. This is illustrated in the following table showing approximate equilibrium percentages for butenes at various temperatures:

Butene-2, Wt. Butene-l, percent Temp, C. Wt.

percent Cis Trans Total 2,956,094 Patented Oct. 11, 1960 maximum conversions are achieved at temperatures be-s low 100 C., e.g., about 40 to 100 C.

To isomerize straight-chain terminal olefins to straightspite extensive exploratory research, have heretofore never been recognized or employed for such purpose. In

carrying out the novel process for the invention, the

straight-chain terminal olefin or olefins to be isomerized are contacted with the alkanesulfonic acid at a tempera:

ture of above about 40 C., e.g., 40 to 100 C., and the resulting internal olefin or olefins separated therefrom by ordinary means, such as, for example, flashing, distillation, decantation, chemical separation, and the like. The invention is advantageously employed to convert such terminal olefins as butene-l, pentene-l, hexene-l, heptene-l, octene-l, nonene-l, decene-l, undecene-l, dodecene-l, and the like.

Examples of alkanesulfonic acids which may be employed in the present invention are methanesulfonic acid,

ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexansulfonic acid, heptanesulfonic acid, octanesulfonic acid, nonanesulfonic acid, decanesulfonic acid, and so forth, including mixtures thereof. In general, any of the alkanemonosulfonic acids or mixtures of such acids may be employed in practicing the present invention so long as the acid or mixtures of acids are liquids at the temperatures employed, or are capable of dissolving in the olefin to be isomerized at the temperatures to be employed. Because of ready availability on the commercial market, we usually employ methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, or mixtures of two or more thereof.

Effective conversions (e.g., above percent of equilibrium) may be carried out at C. or higher. The upper temperature is limited only by decomposition and/or vaporization considerations which, in general, may be ignored since substantially lower temperatures are normally preferred to take advantage of more-favorable equilibrium conditions. Thus, to operate under favorable equilibrium conditions and to obtain maximum conversion, we usually operate at a temperature of about 40 to 100 0, preferably 50 to 80 C. Atmospheric pressure and pressures higher or lower than atmospheric may also be used, e.g., 0.1 to 100 atmospheres. When carrying out the process batchwise, we prefer to use sufiicient pressure to maintain the olefin as a liquid so that both the catalyst and the olefin are in liquid phase. Thus, in the case of butenes, for example, pressures of at least about 35 atmospheres are normally employed. It should be understood, however, that it is only necessary that the alkanesulfonic acid be in the liquid phase since satisfactory conversions may be obtained by contacting the alkanesulfonic acid with gaseous external olefin, for example by bubbling the gaseous olefin through the alkanesulfonic acid. In general, we prefer to operate the system at pressures in the range of about 1 to 20 atmospheres.

If the terminal olefin and the alkanesulfonic acid are present, some olefin isomerization generally results regardless of the relative proportions or concentrations of each. In practice, however, we usually use concentrations of the alkanesulfonic acid above at least about 1 mol percent, based on olefin, preferably above about 5 mol percent, and optimally 10 to 200 mol percent. Contact time is usually governed by the degree of isomerization desired, and usually is substantially in excess of about 1 second. The weight hourly space velocity (i.e., weight of olefin per hour per unit weight of alkanesulfonic acid) may vary from about 0.001 to 1000, usually about 0.1

In a particularly advantageous embodiment of the present invention, it has been discovered that reaction rate may be increased by addition to the reaction zone of phosphorus oxychloride as a promoter. The promoter may be added at any point, that is, to the olefin, to the alkanesulfonic acid, or to the mixture of the olefin and alkanesulfonic acid. For significant promotion, at least about 0.1 mol of promoter is required per mol of alkanesulfonic acid. We usually use 0.1 to 100 mols of promoter per mol of alkanesulfonic acid, preferably 1 to mols per mol.

In carrying out our invention we prefer to use ethanesulfonic acid as the catalyst and to operate with the olefin, as well as the catalyst, in liquid phase and, optionally, in the presence of 0.1 to 100 mols of phosphorus oxychloride promoter per mol of ethanesulfonic acid. As previously pointed out, preferred temperatures are in the range of about 50 to 80 C. and pressures in the range of about 1 to 20 atmospheres (but, of course, high enough to maintain the olefin in the liquid phase).

The invention will be more clearly understood from, and illustrated by, the following specific examples.

Example I This example illustrates vapor-phase isomerization by means of the present invention, that is, the reactant, butene-l, was passed through the liquid catalyst at essentially atmospheric pressure. In the first run, methanesulfonic acid was used as catalyst; in the second run, ethanesulfonic acid was used as catalyst. Both runs were carried out at temperatures of 60 C. After minutes of on-stream operation, gaseous product from each run was analyzed for butene-Z by gas chromatographic analysis. The results were as follows:

Catalyst Conversion Approx. to Butene- Space Vel. 2, percent Type Grams of Equilibiium Methanesulionic Acid 100 0.5 35 Ethanesulionic Acid 121 0.02 98 The above data illustrate the substantial conversion of butene-l to butene-2 even when the butene-l is introduced as a gas, i.e., with minimum contact time.

Example II This example illustrates the effect of temperature on conversion. Butene-1 was passed through cc. of ethanesulfonic acid at essentially atmospheric pressure and gaseous product analyzed for butene-2 by gas chromatographic analysis. Conversion to butene-Z at two different temperature levels (but at approximately the same space velocity) was as follows:

Conversion to butene2, Temperature, C. percent of equilibrium The above data indicate that temperatures above room temperature (25 C.) are required to obtain substantial conversion of butene-l to butane-2.

Example III butene-2 by gas chromatographic analysis and gave the following results:

Conversion to butene-2,

Time, minutes percent of equilibrium The above data show that, in batch contacting, conversion increases substantially with contact time.

Example IV A series of cycles was made wherein the same catalyst was used over and over again and butene-l was employed as feed. The butene-l was maintained in liquid phase in a closed reaction vessel at a pressure of about 6 atmospheres. The catalyst charge was 36 grams of ethanesulfonic acid and each cycle was carried out at 60 C. In the first cycle, 18 grams of butene-l was charged; in each succeeding cycle, 9 grams of butene-l was charged. Product, containing isomerized olefin, was separated by flashing at atmospheric pressure and analyzed for butene-2 by gas chromatographic analysis with the following results:

Conversion Cycle Time, to Butane-2,

Minutes Percent of Equilibrium The above data illustrate that even after successive use the catalyst is capable of very high conversions.

Example V This example illustrates the embodiment of the invention wherein phosphorus oxychloride is employed as a promoter, as compared with results obtained without promoter. In each set of runs, 10 cc. of ethanesulfonic acid was employed as catalyst at a pressure of about 6 atmospheres and at a temperature of 60 C. In each cycle of each set of runs 30 cc. of butene-l was employed as feedstock. For the set of runs wherein promoter was employed, 34 grams of phosphorus oxychloride was added to the ethanesulfonic acid at the beginning of the first cycle. Product, containing isomerized olefin, was separated by flashing and analyzed by gas chromatographic analysis with the following results:

Promoter Cycle Time,

Minutes It is evident from the above data that the phosphorus oxychloride promoter greatly increased the rate of reaction in both the first and second cycles as compared with the first and second cycles without promoter.

Example Vl It is evident from the above data that the conversion obtained with the catalyst of the present invention in onefifth the time was more than twice that of the other catalysts.

Example VII This example illustrates use of the catalyst of the pressent invention for converting octene-1 to internal octene. 30 cc. of octene-1 was contacted with cc. of ethanesulfonic acid for 16 hours at essentially atmospheric pressure and at a temperature of about 60 C. The C fraction in the product was isolated and analyzed for internal octene by infrared analysis. The results showed about 40% of equilibrium internal octene with over 95% of said internal octene being the desirable trans type.

In none of the above examples did excessive cracking or polymerization of olefin occur. Even though relatively low temperatures are employed, high conversion and conversion rates are obtained. The conversion and conversion rates can be improved still further by introducing phosphorus oxychloride promoter. Alkanesulionic acids (as well as phosphorus oxychloride) are readily-available commercially at reasonable cost and do not require high purification (e.g., drying) of feedstock or introduce excessive contaminants into isomerized product. Thus, it is apparent that the objects of the present invention have been achieved.

While the invention has been described in connection with certain specific embodiments it is to be understood that such embodiments are illustrative only, and not by way of limitation. Numerous additional embodiments of the invention and alternative manipulative techniques and operating conditions will be apparent from the foregoing description to those skilled in the art.

Having thus described the invention in detail, what is claimed is:

1. An improved process for isomerizing a straightchain terminal olefin to a straight-chain internal olefin which comprises contacting the terminal olefin with a catalyst consisting essentially of an alkanesulfonic acid at a temperature above about 40 C., and separating the resulting internal olefin therefrom.

2. The process of claim 1 wherein said alkanesulfonic acid is methanesulfonic acid.

3. The process of claim 1 wherein said alkanesulfonic acid is ethanesulfonic acid.

4. The process of claim 1 wherein the contacting step is promoted by addition of 0.1 to 100 mols of phosphorus oxychloride per mol of alkanesulfonic acid.

5. An improved process for isomerizing a straight-chain terminal olefin to a straight-chain internal olefin which comprises contacting the terminal olefin at a temperature of about 40 to C. and a pressure of about 0.1 to 100 atmospheres with a catalyst consisting essentially of an alkanesulfonic acid, and separating the resulting internal olefin therefrom.

6. The method of claim 5 wherein said alkanesulfonic acid is methanesulfonic acid.

7. The process of claim 5 wherein alkanesulfonic acid is ethanesulfonic acid.

8. The process of claim 5 wherein the contacting step is carried out in the presence of 0.1 to 100 mols of phosphorus oxychloride per mol of alkanesulfonic acid.

9. An improved process for isomerizing straight-chain terminal olefins to straight-chain internal olefins which comprises contacting the terminal olefin at a temperature of about 40 to 100 C. and a pressure of 0.1 to 100 atmospheres with a catalyst consisting essentially of at least about 1 mol percent, based on olefin, of an alkanesulfonic acid, and separating the resulting internal olefin therefrom.

10. An improved process for isomerizing straight-chain terminal olefins to straight-chain internal olefins which comprises contacting the terminal olefins at a temperature of about 40 to 100 C. and a pressure of about 0.1 to 100 atmospheres with a catalyst consisting essentially of an alkanesulfonic acid in the presence of about 0.1 to 100 mols of phosphorus oxychloride per mol of alkanesulfonic acid, and separating the resulting internal olefins therefrom.

11. An improved process for isomerizing butene-l to butene-2 which comprises contacting the butene-l at a temperature of about 40 to 100 C. and a pressure of about 1 to 20 atmospheres with a catalyst consisting essentially of above about 1 mol percent, based on butenes, of an alkanesulfonic acid, and separating the resulting butene-2 therefrom.

12. An improved process for isomerizing butene-l to butene-Z which comprises contacting the butene-l at a temperature of about 40 to 100 C. and a pressure of about 1 to 20 atmospheres with a catalyst consisting essentially of above about 1 mol percent, based on butenes, of ethanesulfonic acid in the presence of 0.1 to 100 mols of phosphorus oxychloride per mol of ethanesulfonic acid, and separating the resulting internal olefins therefrom.

13. A catalyst for isomerizing straight-chain terminal olefins to straight-chain internal olefins consisting essentially of an alkanesulfonic acid and 0.1 to 100 mols of phosphorus oxychloride per mol of alkanesulfonic acid.

14. The catalyst of claim 13 wherein said alkanesulfonic acid is methanesulfonic acid.

15. The catalyst of claim 13 wherein said alkanesulfonic acid is ethanesulfonic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,403,439 Ipatieif et a1. July 9, 1946 2,404,340 Zimmerman July 16, 1946 2,641,600 Harban et al June 9, 1953 2,731,502 Smith Jan. 17, 1956 

1. AN IMPROVED PROCESS FOR ISOMERIZING A STRAIGHTCHAIN TERMINAL OLEFIN TO A STRAIGHT-CHAIN INTERNAL OLEFIN WHICH COMPRISES CONTACTING THE TERMINAL OLEFIN WITH A CATALYST CONSISTING ESSENTIALLY OF AN ALKANESULFONIC ACID AT A TEMPERATURE ABOVE ABOUT 40*C., AND SEPARATING THE RESULTING INTERNAL OLEFIN THEREFROM. 